Synthesis of thiohydantoins

ABSTRACT

A novel synthesis of the anti-androgen, A52, which has been found to be useful in the treatment of prostate cancer, is provided. A52 as well as structurally related analogs may be prepared via the inventive route. This new synthetic scheme may be used to prepare kilogram scale quantities of pure A52.

RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119(e) to U.S.provisional patent applications, U.S. Ser. No. 60/908,280, filed Mar.27, 2007, and U.S. Ser. No. 60/909,195, filed Mar. 30, 2007, each ofwhich is incorporated herein by reference.

GOVERNMENT SUPPORT

This invention was made with U.S. Government support under grant numberP01 129243 awarded by the National Cancer Institute. The U.S. Governmenthas certain rights in the invention.

BACKGROUND OF THE INVENTION

Prostate cancer is one of the most common forms of cancer found inWestern men and the second leading cause of cancer death in Western men.When prostate cancer is confined locally, the disease can usually betreated by surgery and/or radiation. Advanced disease is frequentlytreated with anti-androgen therapy, also known as androgen deprivationtherapy. Administration of anti-androgens blocks androgen receptor (AR)function by competing for androgen binding; and therefore, anti-androgentherapy reduces AR activity. Frequently, such therapy fails after atime, and the cancer becomes hormone refractory, that is, the prostatecancer no longer responds to hormone therapy and the cancer does notrequire androgens to progress.

Overexpression of AR has been identified as a cause of hormonerefractory prostate cancer (Nat. Med., 10:33-39, 2004; incorporatedherein by reference). Overexpression of AR is sufficient to causeprogression from hormone sensitive to hormone refractory prostatecancer, suggesting that better AR antagonists than the current drugs maybe able to slow the progression of prostate cancer. It has beendemonstrated that overexpression of AR converts anti-androgens fromantagonists to agonists in hormone refractory prostate cancer. This workexplains why anti-androgen therapy fails to prevent the progression ofprostate cancer.

The identification of compounds that have a high potency to anatgonizeAR activity would overcome the hormone refractory prostate cancer andslowdown the progression of hormone sensitive prostate cancer. Suchcompounds have been identified by Sayers et al. (WO 2007/126765,published Nov. 8, 2007; which is incorporated herein by reference). Onecompound is known as A52, a biarylthiohydantoin, and has the chemicalstructure:

Another compound A51 has the chemical structure:

Both of these compounds share the same western and central portions.Given the need for larger quantities of pure A51 and A52 forpre-clinical and clinical studies, there remains a need for a moreefficient synthesis of the compound from commercially available startingmaterials.

SUMMARY OF THE INVENTION

The present invention provides synthetic methodology and usefulintermediates for preparing thiohydantoins. The inventive methodology isparticularly useful in the synthesis of biarylthiohydantoins In certainembodiments, the compounds are anti-androgen compounds useful in thetreatment of cancer, such as A51 and A52. The inventive synthesisprovides routes to useful intermediates in the synthesis of thesecompounds as well as the final product (e.g., A51, A52). In particular,the invention provides a more efficient to A52 than was previouslyknown. The synthesis is based on the retrosynthetic analysis of theexemplary compound A52 as shown in FIG. 1. In particular, twointermediates,3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile and4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide, are preparedand coupled together to form the compound A52. As would be appreciatedby one of skill in the art, the synthetic methods and intermediates maybe modified to prepare analogs of A52 such as otherbiarylthiohydantoins.

In one aspect, the invention provides a novel synthesis of3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile. In certainembodiments, the method of synthesizing3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile comprises:

(a) chlorinating a 5-nitropyridine of formula:

under suitable conditions (e.g., POCl₃/PCl₅) to provide a compound offormula:

(b) cyanating the resulting 2-chloropyridine of step (a) under suitableconditions (e.g., a palladium catalyst and source of cyanide) to providea compound of formula:

(c) reducing the nitro group of the compound from step (b) undersuitable conditions (e.g., iron powder) to provide an amine of formula:

and

(d) converting the amino of step (c) under suitable conditions (e.g.,thiophosgene) to the corresponding isothiocyanate of formula:

In certain embodiments, the method of synthesizing3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile comprises:

(a) halogenating a compound of formula:

under suitable conditions (e.g., N-iodosuccinimide orN-bromosuccinimide) to provide a compound of formula:

wherein X is bromine or iodine;

(b) chlorinating the resulting halogenated compound of step (a) undersuitable conditions (e.g., POCl₃) to provide a compound of formula:

wherein X is bromine or iodine;

(c) aminating the resulting compound of step (b) under suitableconditions (e.g., palladium catalyst and amine) to provide a compound offormula:

(d) cyanating the resulting 2-chloropyridine of step (c) under suitableconditions (e.g., palladium catalyst and source of CN) to provide acompound of formula:

(e) deprotecting the resulting amine of step (d) under suitableconditions (e.g., TFA) to provide a compound of formula:

and

(f) converting the 5-aminopyridine of step (e) under suitable conditions(e.g., thiophosgene) to the corresponding isothiocyanate of formula:

In another aspect, the invention provides a synthesis of4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide. In certainembodiments, the method of synthesizing4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide comprisesreacting a compound of formula:

wherein R₁ is a substituted or unsubstituted acyl moiety or —CN, with

under suitable conditions to provide a compound of formula:

In certain embodiments, the method of synthesizing4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide comprisesreacting a compound of formula:

wherein R₁ is a substituted or unsubstituted acyl moiety or —CN, with

and a source of cyanide (CN) under suitable conditions to provide acompound of formula:

In another aspect, the present invention provides a method ofsynthesizing A52 by coupling3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile with4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide. In certainembodiments, the synthetic method comprises coupling a substitutedpyridine of formula:

with a compound of formula:

under suitable conditions to form a product of formula:

The final product may be purified by recrystallization from ethanol toprovide pure material suitable for pre-clinical or clinical studies. Thesynthetic methodology described herein may be scaled up to produce 1 kgor more of pure A52.

In another aspect, the present invention provides novel intermediatesuseful in the synthesis of A52. In certain embodiments, the intermediateis of formula:

In certain embodiments, the intermediate is of the formula:

wherein X is halogen. In certain embodiments, the intermediate is of theformula:

wherein X is halogen or —CN.

The novel synthesis of A52 and analogues thereof provides pure compoundin a more efficient route than previous syntheses of this compound. Theinventive syntheses are scalable allowing for the production of kilogramquantities of the desired final product.

DEFINITIONS

Definitions of specific functional groups and chemical terms aredescribed in more detail below. For purposes of this invention, thechemical elements are identified in accordance with the Periodic Tableof the Elements, CAS version, Handbook of Chemistry and Physics, 75^(th)Ed., inside cover, and specific functional groups are generally definedas described therein. Additionally, general principles of organicchemistry, as well as specific functional moieties and reactivity, aredescribed in Organic Chemistry, Thomas Sorrell, University ScienceBooks, Sausalito: 1999, the entire contents of which are incorporatedherein by reference.

Certain compounds of the present invention may exist in particulargeometric or stereoisomeric forms. The present invention contemplatesall such compounds, including cis- and trans-isomers, R- andS-enantiomers, diastereomers, (D)-isomers, (L)-isomers, the racemicmixtures thereof, and other mixtures thereof, as falling within thescope of the invention. Additional asymmetric carbon atoms may bepresent in a substituent such as an alkyl group. All such isomers, aswell as mixtures thereof, are intended to be included in this invention.

Isomeric mixtures containing any of a variety of isomer ratios may beutilized in accordance with the present invention. For example, whereonly two isomers are combined, mixtures containing 50:50, 60:40, 70:30,80:20, 90:10, 95:5, 96:4, 97:3, 98:2, 99:1, or 100:0 isomer ratios areall contemplated by the present invention. Those of ordinary skill inthe art will readily appreciate that analogous ratios are contemplatedfor more complex mixtures of isomers.

If, for instance, a particular enantiomer of a compound of the presentinvention is desired, it may be prepared by asymmetric synthesis, or byderivation with a chiral auxiliary, where the resulting diastereomericmixture is separated and the auxiliary group cleaved to provide the puredesired enantiomer or diastereomer. Alternatively, where the moleculecontains a basic functional group, such as an amino group, or an acidicfunctional group, such as a carboxylic acid group, diastereomeric saltsare formed with an appropriate optically-active acid or base, followedby resolution of the diastereomers thus formed by fractionalcrystallization or chromatographic means well known in the art, andsubsequent recovery of the pure enantiomers.

One of ordinary skill in the art will appreciate that the syntheticmethods, as described herein, utilize a variety of protecting groups. Bythe term “protecting group,” as used herein, it is meant that aparticular functional moiety, e.g., O, S, or N, is masked or blocked,permitting, if desired, a reaction to be carried out selectively atanother reactive site in a multifunctional compound. In preferredembodiments, a protecting group reacts selectively in good yield to givea protected substrate that is stable to the projected reactions; theprotecting group is preferably selectively removable by readilyavailable, preferably non-toxic reagents that do not attack the otherfunctional groups; the protecting group forms a separable derivative(more preferably without the generation of new stereogenic centers); andthe protecting group will preferably have a minimum of additionalfunctionality to avoid further sites of reaction. As detailed herein,oxygen, sulfur, nitrogen, and carbon protecting groups may be utilized.By way of non-limiting example, hydroxyl protecting groups includemethyl, methoxylmethyl (MOM), methylthiomethyl (MTM), t-butylthiomethyl,(phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM),p-methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM),guaiacolmethyl (GUM), t-butoxymethyl, 4-pentenyloxymethyl (POM),siloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl,bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR),tetrahydropyranyl (THP), 3-bromotetrahydropyranyl,tetrahydrothiopyranyl, 1-methoxycyclohexyl, 4-methoxytetrahydropyranyl(MTHP), 4-methoxytetrahydrothiopyranyl, 4-methoxytetahydrothiopyranylS,S-dioxide, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl(CTMP), 1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl,1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl,1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl,2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl,t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl,benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl,p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl,p-phenylbenzyl, 2-picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxido,diphenylmethyl, p,p′-dinitrobenzhydryl, 5-dibenzosuberyl,triphenylmethyl, α-naphthyldiphenylmethyl,p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl,tri(p-methoxyphenyl)methyl,4,4′,4″-bromophenacyloxyphenyl)diphenylmethyl,4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl,4,4′,4″-tris(levulinoyloxyphenyl)methyl,4,4′,4″-tris(benzoyloxyphenyl)methyl,3-(imidazol-1-yl)bis(4′,4″-dimethoxyphenyl)methyl,1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl,9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl,1,3-benzodithiolan-2-yl, benzisothiazolyl S,S-dioxido, trimethylsilyl(TMS), triethylsilyl (TES), triisopropylsilyl (TIPS),dimethylisopropylsilyl (IPDMS), diethylisopropylsilyl (DEIPS),dimethylthexylsilyl, t-butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl(TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl,diphenylmethylsilyl (DPMS), t-butylmethoxyphenylsilyl (TBMPS), formate,benzoylformate, acetate, chloroacetate, dichloroacetate,trichloroacetate, trifluoroacetate, methoxyacetate,triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate,3-phenylpropionate, 4-oxopentanoate (levulinate),4,4-(ethylenedithio)pentanoate (levulinoyldithioacetal), pivaloate,adamantoate, crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate,2,4,6-trimethylbenzoate (mesitoate), alkyl methyl carbonate,9-fluorenylmethyl carbonate (Fmoc), alkyl ethyl carbonate, alkyl2,2,2-trichloroethyl carbonate (Troc), 2-(trimethylsilyl)ethyl carbonate(TMSEC), 2-(phenylsulfonyl)ethyl carbonate (Psec),2-(triphenylphosphonio) ethyl carbonate (Peoc), alkyl isobutylcarbonate, alkyl vinyl carbonate alkyl allyl carbonate, alkylp-nitrophenyl carbonate, alkyl benzyl carbonate, alkyl p-methoxybenzylcarbonate, alkyl 3,4-dimethoxybenzyl carbonate, alkyl o-nitrobenzylcarbonate, alkyl p-nitrobenzyl carbonate, alkyl S-benzyl thiocarbonate,4-ethoxy-1-napththyl carbonate, methyl dithiocarbonate, 2-iodobenzoate,4-azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate,2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl,4-(methylthiomethoxy)butyrate, 2-(methylthiomethoxymethyl)benzoate,2,6-dichloro-4-methylphenoxyacetate,2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate,2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate,isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate,o-(methoxycarbonyl)benzoate, α-naphthoate, nitrate, alkylN,N,N′,N′-tetramethylphosphorodiamidate, alkyl N-phenylcarbamate,borate, dimethylphosphinothioyl, alkyl 2,4-dinitrophenylsulfenate,sulfate, methanesulfonate (mesylate), benzylsulfonate, and tosylate(Ts). For protecting 1,2- or 1,3-diols, the protecting groups includemethylene acetal, ethylidene acetal, 1-t-butylethylidene ketal,1-phenylethylidene ketal, (4-methoxyphenyl)ethylidene acetal,2,2,2-trichloroethylidene acetal, acetonide, cyclopentylidene ketal,cyclohexylidene ketal, cycloheptylidene ketal, benzylidene acetal,p-methoxybenzylidene acetal, 2,4-dimethoxybenzylidene ketal,3,4-dimethoxybenzylidene acetal, 2-nitrobenzylidene acetal,methoxymethylene acetal, ethoxymethylene acetal, dimethoxymethyleneortho ester, 1-methoxyethylidene ortho ester, 1-ethoxyethylidine orthoester, 1,2-dimethoxyethylidene ortho ester, α-methoxybenzylidene orthoester, 1-(N,N-dimethylamino)ethylidene derivative,α-(N,N′-dimethylamino)benzylidene derivative, 2-oxacyclopentylideneortho ester, di-t-butylsilylene group (DTBS),tetraisopropyldisiloxanylidene) derivative (TIPDS),tetra-t-butoxydisiloxane-1,3-diylidene derivative (TBDS), cycliccarbonates, cyclic boronates, ethyl boronate, and phenyl boronate.Amino-protecting groups include methyl carbamate, ethyl carbamante,9-fluorenylmethyl carbamate (Fmoc), 9-(2-sulfo)fluorenylmethylcarbamate, 9-(2,7-dibromo)fluoroenylmethyl carbamate,2,7-di-t-butyl-[9-(10,10-dioxo-10,10,10,10-tetrahydrothioxanthyl)]methylcarbamate (DBD-Tmoc), 4-methoxyphenacyl carbamate (Phenoc),2,2,2-trichloroethyl carbamate (Troc), 2-trimethylsilylethyl carbamate(Teoc), 2-phenylethyl carbamate (hZ), 1-(1-adamantyl)-1-methylethylcarbamate (Adpoc), 1,1-dimethyl-2-haloethyl carbamate,1,1-dimethyl-2,2-dibromoethyl carbamate (DB-t-BOC),1,1-dimethyl-2,2,2-trichloroethyl carbamate (TCBOC),1-methyl-1-(4-biphenylyl)ethyl carbamate (Bpoc),1-(3,5-di-t-butylphenyl)-1-methylethyl carbamate (t-Bumeoc), 2-(2′- and4′-pyridyl)ethyl carbamate (Pyoc), 2-(N,N-dicyclohexylcarboxamido)ethylcarbamate, t-butyl carbamate (BOC), 1-adamantyl carbamate (Adoc), vinylcarbamate (Voc), allyl carbamate (Alloc), 1-isopropylallyl carbamate(Ipaoc), cinnamyl carbamate (Coc), 4-nitrocinnamyl carbamate (Noc),8-quinolyl carbamate, N-hydroxypiperidinyl carbamate, alkyldithiocarbamate, benzyl carbamate (Cbz), p-methoxybenzyl carbamate (Moz),p-nitobenzyl carbamate, p-bromobenzyl carbamate, p-chlorobenzylcarbamate, 2,4-dichlorobenzyl carbamate, 4-methylsulfinylbenzylcarbamate (Msz), 9-anthrylmethyl carbamate, diphenylmethyl carbamate,2-methylthioethyl carbamate, 2-methylsulfonylethyl carbamate,2-(p-toluenesulfonyl)ethyl carbamate, [2-(1,3-dithianyl)]methylcarbamate (Dmoc), 4-methylthiophenyl carbamate (Mtpc),2,4-dimethylthiophenyl carbamate (Bmpc), 2-phosphonioethyl carbamate(Peoc), 2-triphenylphosphonioisopropyl carbamate (Ppoc),1,1-dimethyl-2-cyanoethyl carbamate, m-chloro-p-acyloxybenzyl carbamate,p-(dihydroxyboryl)benzyl carbamate, 5-benzisoxazolylmethyl carbamate,2-(trifluoromethyl)-6-chromonylmethyl carbamate (Tcroc), m-nitrophenylcarbamate, 3,5-dimethoxybenzyl carbamate, o-nitrobenzyl carbamate,3,4-dimethoxy-6-nitrobenzyl carbamate, phenyl(o-nitrophenyl)methylcarbamate, phenothiazinyl-(10)-carbonyl derivative,N′-p-toluenesulfonylaminocarbonyl derivative, N′-phenylaminothiocarbonylderivative, t-amyl carbamate, S-benzyl thiocarbamate, p-cyanobenzylcarbamate, cyclobutyl carbamate, cyclohexyl carbamate, cyclopentylcarbamate, cyclopropylmethyl carbamate, p-decyloxybenzyl carbamate,2,2-dimethoxycarbonylvinyl carbamate, o-(N,N-dimethylcarboxamido)benzylcarbamate, 1,1-dimethyl-3-(N,N-dimethylcarboxamido)propyl carbamate,1,1-dimethylpropynyl carbamate, di(2-pyridyl)methyl carbamate,2-furanylmethyl carbamate, 2-iodoethyl carbamate, isoborynl carbamate,isobutyl carbamate, isonicotinyl carbamate,p-(p′-methoxyphenylazo)benzyl carbamate, 1-methylcyclobutyl carbamate,1-methylcyclohexyl carbamate, 1-methyl-1-cyclopropylmethyl carbamate,1-methyl-1-(3,5-dimethoxyphenyl)ethyl carbamate,1-methyl-1-(p-phenylazophenyl)ethyl carbamate, 1-methyl-1-phenylethylcarbamate, 1-methyl-1-(4-pyridyl)ethyl carbamate, phenyl carbamate,p-(phenylazo)benzyl carbamate, 2,4,6-tri-t-butylphenyl carbamate,4-(trimethylammonium)benzyl carbamate, 2,4,6-trimethylbenzyl carbamate,formamide, acetamide, chloroacetamide, trichloroacetamide,trifluoroacetamide, phenylacetamide, 3-phenylpropanamide, picolinamide,3-pyridylcarboxamide, N-benzoylphenylalanyl derivative, benzamide,p-phenylbenzamide, o-nitophenylacetamide, o-nitrophenoxyacetamide,acetoacetamide, (N′-dithiobenzyloxycarbonylamino)acetamide,3-(p-hydroxyphenyl)propanamide, 3-(o-nitrophenyl)propanamide,2-methyl-2-(o-nitrophenoxy)propanamide,2-methyl-2-(o-phenylazophenoxy)propanamide, 4-chlorobutanamide,3-methyl-3-nitrobutanamide, o-nitrocinnamide, N-acetylmethioninederivative, o-nitrobenzamide, o-(benzoyloxymethyl)benzamide,4,5-diphenyl-3-oxazolin-2-one, N-phthalimide, N-dithiasuccinimide (Dts),N-2,3-diphenylmaleimide, N-2,5-dimethylpyrrole,N-1,1,4,4-tetramethyldisilylazacyclopentane adduct (STABASE),5-substituted 1,3-dimethyl-1,3,5-triazacyclohexan-2-one, 5-substituted1,3-dibenzyl-1,3,5-triazacyclohexan-2-one, 1-substituted3,5-dinitro-4-pyridone, N-methylamine, N-allylamine,N-[2-(trimethylsilyl)ethoxy]methylamine (SEM), N-3-acetoxypropylamine,N-(1-isopropyl-4-nitro-2-oxo-3-pyroolin-3-yl)amine, quaternary ammoniumsalts, N-benzylamine, N-di(4-methoxyphenyl)methylamine,N-5-dibenzosuberylamine, N-triphenylmethylamine (Tr),N-[(4-methoxyphenyl)diphenylmethyl]amine (MMTr),N-9-phenylfluorenylamine (PhF),N-2,7-dichloro-9-fluorenylmethyleneamine, N-ferrocenylmethylamino (Fcm),N-2-picolylamino N′-oxide, N-1,1-dimethylthiomethyleneamine,N-benzylideneamine, N-p-methoxybenzylideneamine,N-diphenylmethyleneamine, N-[(2-pyridyl)mesityl]methyleneamine,N-(N′,N′-dimethylaminomethylene)amine, N,N′-isopropylidenediamine,N-p-nitrobenzylideneamine, N-salicylideneamine,N-5-chlorosalicylideneamine,N-(5-chloro-2-hydroxyphenyl)phenylmethyleneamine,N-cyclohexylideneamine, N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)amine,N-borane derivative, N-diphenylborinic acid derivative,N-[phenyl(pentacarbonylchromium- or tungsten)carbonyl]amine, N-copperchelate, N-zinc chelate, N-nitroamine, N-nitrosoamine, amine N-oxide,diphenylphosphinamide (Dpp), dimethylthiophosphinamide (Mpt),diphenylthiophosphinamide (Ppt), dialkyl phosphoramidates, dibenzylphosphoramidate, diphenyl phosphoramidate, benzenesulfenamide,o-nitrobenzenesulfenamide (Nps), 2,4-dinitrobenzenesulfenamide,pentachlorobenzenesulfenamide, 2-nitro-4-methoxybenzenesulfenamide,triphenylmethylsulfenamide, 3-nitropyridinesulfenamide (Npys),p-toluenesulfonamide (Ts), benzenesulfonamide,2,3,6-trimethyl-4-methoxybenzenesulfonamide (Mtr),2,4,6-trimethoxybenzenesulfonamide (Mtb),2,6-dimethyl-4-methoxybenzenesulfonamide (Pme),2,3,5,6-tetramethyl-4-methoxybenzenesulfonamide (Mte),4-methoxybenzenesulfonamide (Mbs), 2,4,6-trimethylbenzenesulfonamide(Mts), 2,6-dimethoxy-4-methylbenzenesulfonamide (iMds),2,2,5,7,8-pentamethylchroman-6-sulfonamide (Pmc), methanesulfonamide(Ms), β-trimethylsilylethanesulfonamide (SES), 9-anthracenesulfonamide,4-(4′,8′-dimethoxynaphthylmethyl)benzenesulfonamide (DNMBS),benzylsulfonamide, trifluoromethylsulfonamide, and phenacylsulfonamide.Exemplary protecting groups are detailed herein, however, it will beappreciated that the present invention is not intended to be limited tothese protecting groups; rather, a variety of additional equivalentprotecting groups can be readily identified using the above criteria andutilized in the method of the present invention. Additionally, a varietyof protecting groups are described in Protective Groups in OrganicSynthesis, Third Ed., Greene, T. W. and Wuts, P. G., Eds., John Wiley &Sons, New York: 1999, the entire contents of which are herebyincorporated by reference.

It will be appreciated that the compounds, as described herein, may besubstituted with any number of substituents or functional moieties. Ingeneral, the term “substituted” whether preceded by the term“optionally” or not, and substituents contained in formulas of thisinvention, refer to the replacement of hydrogen radicals in a givenstructure with the radical of a specified substituent. When more thanone position in any given structure may be substituted with more thanone substituent selected from a specified group, the substituent may beeither the same or different at every position. As used herein, the term“substituted” is contemplated to include all permissible substituents oforganic compounds. In a broad aspect, the permissible substituentsinclude acyclic and cyclic, branched and unbranched, carbocyclic andheterocyclic, aromatic and nonaromatic substituents of organiccompounds. For purposes of this invention, heteroatoms such as nitrogenmay have hydrogen substituents and/or any permissible substituents oforganic compounds described herein which satisfy the valencies of theheteroatoms. Furthermore, this invention is not intended to be limitedin any manner by the permissible substituents of organic compounds.Combinations of substituents and variables envisioned by this inventionare preferably those that result in the formation of stable compoundsuseful in the treatment, for example, of infectious diseases orproliferative disorders. The term “stable”, as used herein, preferablyrefers to compounds which possess stability sufficient to allowmanufacture and which maintain the integrity of the compound for asufficient period of time to be detected and preferably for a sufficientperiod of time to be useful for the purposes detailed herein.

In general, the terms “aryl” and “heteroaryl”, as used herein, refer tostable mono- or polycyclic, heterocyclic, polycyclic, andpolyheterocyclic unsaturated moieties having preferably 3-14 carbonatoms, each of which may be substituted or unsubstituted. Substituentsinclude, but are not limited to, any of the previously mentionedsubstitutents, i.e., the substituents recited for aliphatic moieties, orfor other moieties as disclosed herein, resulting in the formation of astable compound. In certain embodiments of the present invention, “aryl”refers to a mono- or bicyclic carbocyclic ring system having one or twoaromatic rings including, but not limited to, phenyl, naphthyl,tetrahydronaphthyl, indanyl, indenyl, and the like. In certainembodiments of the present invention, the term “heteroaryl”, as usedherein, refers to a cyclic aromatic radical having from five to ten ringatoms of which one ring atom is selected from S, O, and N; zero, one, ortwo ring atoms are additional heteroatoms independently selected from S,O, and N; and the remaining ring atoms are carbon, the radical beingjoined to the rest of the molecule via any of the ring atoms, such as,for example, pyridyl, pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl,imidazolyl, thiazolyl, oxazolyl, isooxazolyl, thiadiazolyl, oxadiazolyl,thiophenyl, furanyl, quinolinyl, isoquinolinyl, and the like.

It will be appreciated that aryl and heteroaryl groups can beunsubstituted or substituted, wherein substitution includes replacementof one, two, three, or more of the hydrogen atoms thereon independentlywith any one or more of the following moieties including, but notlimited to: aliphatic; heteroaliphatic; aryl; heteroaryl; arylalkyl;heteroarylalkyl; alkoxy; aryloxy; heteroalkoxy; heteroaryloxy;alkylthio; arylthio; heteroalkylthio; heteroarylthio; —F; —Cl; —Br; —I;—OH; —NO₂; —CN; —CF₃; —CH₂CF₃; —CHCl₂; —CH₂OH; —CH₂CH₂OH; —CH₂NH₂;—CH₂SO₂CH₃; —C(O)R_(x); —CO₂(R_(x)); —CON(R_(x))₂; —OC(O)R_(x);—OCO₂R_(x); —OCON(R_(x))₂; —N(R_(x))₂; —S(O)₂R_(x); —NR_(x)(CO)R_(x),wherein each occurrence of R_(x) independently includes, but is notlimited to, aliphatic, heteroaliphatic, aryl, heteroaryl, arylalkyl, orheteroarylalkyl, wherein any of the aliphatic, heteroaliphatic,arylalkyl, or heteroarylalkyl substituents described above and hereinmay be substituted or unsubstituted, branched or unbranched, cyclic oracyclic, and wherein any of the aryl or heteroaryl substituentsdescribed above and herein may be substituted or unsubstituted.Additional examples of generally applicable substitutents areillustrated by the specific embodiments shown in the Examples that aredescribed herein.

The terms “halo” and “halogen” as used herein refer to an atom selectedfrom fluorine, chlorine, bromine, and iodine.

“Independently selected”: The term “independently selected” is usedherein to indicate that the R groups can be identical or different.

“Labeled”: As used herein, the term “labeled” means that a compoundcomprises at least one element, isotope, or chemical compound to enablethe detection of the compound by any technique that would enabledetection. Labels may be: a) isotopic labels, which may be radioactiveor heavy isotopes, including, but not limited to, ²H, ³H, ¹³C, ¹⁴C ¹⁵N,³¹P, ³²P, ³⁵S, ⁶⁷Ga, ^(99m)Tc (Tc-99m), ¹¹¹In, ¹²³I, ¹²⁵I, ¹⁶⁹Yb and¹⁸⁶Re; b) immune labels, which may be antibodies or antigens, which maybe bound to enzymes (such as horseradish peroxidase) that producedetectable agents; or c) colored, luminescent, phosphorescent, orfluorescent dyes. It will be appreciated that the labels incorporatedinto the compound at any position that does not substantially interferewith the biological activity or characteristic of the compound that isbeing detected. In other embodiments such as in the identification ofthe biological target of a natural product or derivative thereof, thecompound is labeled with a radioactive isotope, preferably an isotopewhich emits detectable particles, such as β particles. In certain otherembodiments of the invention, photoaffinity labeling is utilized for thedirect elucidation of intermolecular interactions in biological systems.A variety of known photophores can be employed, most relying onphotoconversion of diazo compounds, azides, or diazirines to nitrenes orcarbenes (see, Bayley, H., Photogenerated Reagents in Biochemistry andMolecular Biology (1983), Elsevier, Amsterdam), the entire contents ofwhich are hereby incorporated by reference. In certain embodiments ofthe invention, the photoaffinity labels employed are o-, m- andp-azidobenzoyls, substituted with one or more halogen moieties,including, but not limited to 4-azido-2,3,5,6-tetrafluorobenzoic acid.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a retrosynthetic analysis of the thiohydantoin, A52.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

A new synthesis of biarylthiohydantoins and intermediates thereto isprovided herein. This new synthetic methodology has been developedspecifically to provide a more efficient synthetic route to theanti-androgen, A52. However, as would be appreciated by an organicchemist, the methodology can also be applied to other compoundsincluding the related compound A51. The synthesis of otherthiohydantoins, particularly biarylthiohydantoins of the formula:

wherein each of R₁ and R₂ is independently a substituted orunsubstituted aryl moiety; or substituted or unsubstituted heteroarylmoiety, may also benefit from the synthetic methods and/or intermediatesdisclosed herein.

Synthesis of Western Portion

As shown in FIG. 1 which includes a retrosynthetic analysis of A52, thecompound is essentially prepared by coupling the two halves of themolecule (compounds A and B) to form the final product. One of the firstimprovements in the synthesis of A52 stems from a shorter and moreefficient synthesis of compound A, which is used for the western portionof the final product. As shown below, Compound A(3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile) isprepared from nitropyridone E by chlorination, palladium-catalyzedcyanation of the resulting chlorine, selective reduction of the nitrogroup, and finally conversion of the resulting amine to anisothiocyanate.

In certain embodiments, the invention provides novel methods ofpreparing compound A from nitropyridone E. In certain embodiments, thesynthetic method includes:

(a) chlorinating a compound of formula:

under suitable conditions (e.g., SOCl₂, POCl₃/PCl₅, POCl₃, PhPOCl₂) toprovide a compound of formula:

(b) cyanating the 2-chloropyridine resulting from step (a) undersuitable conditions (e.g., palladium catalyst and Zn(CN)₂,tri-n-butyltincyanide, Cu(I)CN, potassium hexacyanoferrate (II)) toprovide a compound of formula:

(c) selectively reducing the nitro group of the compound resulting fromstep (b) under suitable conditions (e.g., dissolved Fe(0)) to provide anamine of formula:

and

(d) converting the compound resulting from step (c) under suitableconditions (e.g., thiophosgene in the presence base) to thecorresponding isothiocyanate of formula:

As would be appreciated by one of skill in the art, the aryl ring mayinclude other substituents and the substitution pattern about the ringmay differ from the compounds shown above. In certain embodiments, otheraryl rings besides pyridinyl are used in the above synthetic methods.For example, a phenyl ring or pyrimidinyl ring may be used. Althoughsix-membered aryl rings are shown in the schemes detailed herein,five-membered heteroaryl rings may also be used.

The individual steps in the synthesis of compound A may also beperformed separately in order to prepare compound A or anothersubstituted aromatic compound. As will be appreciated by one of skill inthe art, each of the reaction described herein may optionally befollowed by one or more purification steps (e.g., recrystallization,column chromatography, distillation, extraction, filtration). In certainembodiments, the invention provides a method comprising the step ofchlorinating a 5-hydroxypyridine of formula:

under suitable conditions to provide a compound of formula:

In certain particular embodiments, the chlorination step is performedusing POCl₃/PCl₅. In certain particular embodiments, the chlorinationstep is performed using POCl₃. In certain embodiments, instead of achlorination step, a bromination step is used in the synthesis ofCompound A or the intermediate of formula:

In certain embodiments, the method includes the step of cyanating a2-chloropyridine of formula:

under suitable conditions to provide a compound of formula:

In certain particular embodiments, the cyanation step is apalladium-catalyzed cyanation. In certain embodiments, the palladiumcatalyst is Pd₂(dba)₂ with ligand. In certain embodiments, the palladiumcatalyst is Pd(OAc)₂ with ligand. In certain embodiments, the cyanationstep is performed in the presence of Pd₂(dba)₂, the ligand1,1′-bisdiphenylphosphinoferrocene (dppf), and Zn(CN)₂. In certainembodiments, the amount of catalyst used ranges from about 0.1 mol % toabout 20 mol %. Other palladium catalysts (including ligand) or sourcesof cyanide (e.g., NaCN, KCN, Cu(CN), K₄[Fe(CN)₆], tri-n-butyltincyanide)may also be used. In certain embodiments, the reaction is performed inDMF as the solvent. The reaction may be irradiated with microwaves inorder to effect the transformation. In certain embodiments, the reactionmixture is heated to effect the transformation. In certain embodiments,the reaction is run at a temperature ranging from approximately 100° C.to approximately 150° C. In certain embodiments, the reaction is run atapproximately 130° C. In certain embodiments, a bromopyridine offormula:

is used as the starting material in the inventive cyanation reaction.

In certain embodiments, the method of reducing the nitro group includesselectively reducing the nitro group of a 5-nitropyridine of formula:

under suitable conditions to provide a compound of formula:

This reduction of the nitro group is done in the presence of a nitrilewhich is also susceptible to reduction. Preferably, the conditions ofthe reduction step are such that the nitro group is reduced withoutsubstantially reducing the nitrile group. In certain embodiments, lessthan about 10%, less than about 5%, less than about 2%, or less thanabout 1% of the nitrile groups are reduced. In certain embodiments, thereduction is done with dissolved iron. In certain embodiments, thereduction is performed using iron powder (or other form of iron)dissolved in acetic acid (or other acid such as HCl) and a solvent(e.g., ethyl acetate). In certain embodiments, at least 2 equivalents ofiron are used. In certain embodiments, approximately 5 equivalents ofiron are used. Other metals besides iron may also be used in thisreduction step. In certain embodiments, the reaction is performed atroom temperature. In certain embodiments, the reaction mixture isheated. In certain embodiments, the reaction is performed atapproximately 60-75° C. In certain embodiments, the reaction isperformed at approximately 65° C. In certain embodiments, the reductionof the nitro group is performed using a Raney nickel-catalyzedhydrogenation.

In certain embodiments, the invention provides a method of convertingthe amino group to an isothiocyanate. In certain embodiments, the methodcomprises converting the amino group of a 5-aminopyridine of formula:

under suitable conditions to provide an isothiocyanate of formula:

In certain embodiments, the conversion is performed using thiophosgene.In certain embodiments, the conversion is performed using thiophosgenein the presence of base. This reaction may be carried out in water assolvent at room temperature.

While the above route to Compound A is shorter than those previouslyreported (see WO 2007/126765, published Nov. 8, 2007), yet another routewas developed to provide a better precursor to the amino group atposition 5 of Compound A. This new route begins with2-trifluoromethyl-2-pyridone (C), which is converted into5-iodo-3-trifluoromethyl-2-pyridone or the 5-bromo analog. The halogenanchors the position for the amino group of Compound A. The halogen maybe replaced by another suitable leaving group such as a triflate. Asshown below, Compound A may be prepared by halogenation of 3trifluoromethyl-2-pyridone (C), chlorination of the hydroxyl group, andtwo successive, selective palladium-catalyzed substitutions. The firstpalladium-catalyzed reaction places an amine (e.g., benzylamine,dibenzylamine, 4-methoxybenzylamine, N,N-bis(4-methoxybenzyl)amine) atposition 5. The amine may be unprotected, monoprotected (e.g.,benzylamine), or diprotected (e.g., dibenzylamine). In certainembodiments, the amine is introduced as a free amino group. In certainembodiments, the amine is introduced as a protected amine. The secondintroduces the cyano group. If present, the protecting group on theprotected amine is removed, and the unprotected amino group is convertedto a thiocyanate as described above. While this route requires moresteps, this sequence can be performed on a larger scale than previouslyreported syntheses of Compound A.

In certain embodiments, the invention provides novel methods ofpreparing compound A from 3-trifluoromethyl-2-pyridone C. In certainembodiments, the synthetic method includes the steps of:

(a) halogenating a compound of formula:

under suitable conditions (e.g., N-iodosuccinimide (NIS),N-bromosuccinimide (NBS)) to provide a compound of formula:

wherein X is bromine or iodine;

(b) chlorinating the resulting halogenated compound of step (a) undersuitable conditions (e.g., POCl₃) to provide a compound of formula:

wherein X is bromine or iodine;

(c) aminating the resulting compound of step (b) under suitableconditions (e.g., palladium-catalyzed amination) to provide a compoundof formula:

wherein each PG is independently hydrogen or a suitable amine protectinggroup (e.g., benzyl, methoxybenzyl, 4-methoxybenzyl);

(d) cyanating the resulting 2-chloropyridine of step (c) under suitableconditions (e.g., palladium-catalyzed cyanation) to provide a compoundof formula:

(e) deprotecting the amine of the compound of step (d) under suitableconditions to provide a compound of formula:

and

(f) converting the 5-aminopyridine of step (e) under suitable conditionsto the corresponding isothiocyanate of formula:

As would be appreciated by one of skill in the art, the aryl ring mayinclude other substituents and the substitution pattern about the ringmay differ from the compounds shown above. In certain embodiments, otheraryl rings besides pyridinyl are used in the above synthetic methods.For example, a phenyl ring or pyrimidinyl ring may be used. Althoughsix-membered aryl rings are shown in the schemes detailed herein,five-membered heteroaryl rings may also be used.

The individual steps in this alternative synthesis of compound A mayalso be performed separately in order to prepare compound A or anothersubstituted aromatic compound. For example, in certain embodiments, themethod includes halogenating a substituted pyridine of formula:

under suitable conditions to provide a compound of formula:

wherein X is bromine or iodine. Besides halogens such as bromine andiodine, other suitable leaving groups such as triflate, tosylate, andlike may be used in a subsequent nucleophilic displacement substitution,or transition metal-catalyzed amination, alkyl amination, orcarbamoylation. In the case wherein X is iodine, N-iodosuccinimide (NIS)may be used as the iodinating reagent. In the case wherein X is bromine,N-bromouccinimide (NIS) may be used as the brominating reagent. Incertain embodiments, the halogenation reaction is performed in a mixtureof acetonitrile and DMF at approximately 80° C. In certain embodiments,the solvent for the reaction is acetonitrile:DMF (1:1).

In certain embodiments, the step of converting the hydroxyl group of5-halo-3-trifluoromethyl-2-pyridinol to a chlorine includes chlorinatinga compound of formula:

wherein X is bromine or iodine, under suitable condition to provide acompound of formula:

In certain embodiments, the chlorination reaction is performed usingPOCl₃. In certain embodiments, the chlorination reaction is performedusing POCl₃/PCl₅. In certain embodiments, DMF is used as the solvent inthe chlorination reaction. In certain embodiments, reaction mixture isirradiated with microwaves to effect the chlorination. In certainembodiments, the reaction mixture is heated to a temperature rangingfrom about 100° C. to about 150° C. In certain embodiments, the reactionis heated to approximately 110° C. In certain embodiments, the reactionis heated to approximately 120° C. In certain embodiments, the reactionis heated to approximately 130° C.

In certain embodiments, the iodine, bromine, or other suitable leavinggroup is replaced with an amine via a transition metal-catalyzedreaction (e.g., palladium-catalyzed reaction). In certain embodiments,the method includes aminating a compound of formula:

wherein X is bromine or iodine, under suitable conditions to provide acompound of formula:

wherein each PG is independently hydrogen or a nitrogen protectinggroup. In certain embodiments, the method includes aminating a compoundof formula:

wherein X is bromine or iodine, under suitable conditions to provide acompound of formula:

The amination reaction is preferably selective for position 5. Incertain embodiments, the chlorine at position 2 is unaffected. Othernitrogen-protecting groups besides 4-methoxybenzyl may be used forintroducing the amine. In certain embodiments, the protecting group isbenzyl. In certain embodiments, the protecting group is methoxybenzyl.In certain embodiments, the amine is doubly protected. In certainembodiments, the amine is introduced as an unprotected amino group(—NH₂). In certain embodiments, the amine is introduced as an amide. Incertain embodiments, the amine is introduced as a carbamate. Activeamides, carbamates (e.g., tertiobutylcarbamate, benzylcarbamate), andamines that are deprotected by fluoride ion are also useful. In certainembodiments, the reaction is catalyzed by a palladium catalyst. Incertain embodiments, the reaction is performed in the presence ofPd(OAc)₂, BINAP, Et₃N, and Cs₂CO₃. In certain embodiments, the reactionis performed in the presence of Pd₂(dba)₃, Xantphos, and sodiumtert-butoxide. In certain embodiments, the amount of catalyst usedranges from about 0.1 mol % to about 5 mol %. In certain embodiments,the amine used is 4-methoxybenzylamine. In certain embodiments, thereaction is performed in refluxing toluene. In certain embodiments, thereaction mixture is irradiated with microwaves.

In certain embodiments, the invention provides method of cyanating. Incertain embodiments, the method includes cyanating a compound offormula:

wherein each PG is independently hydrogen or a suitablenitrogen-protecting group, under suitable conditions to provide acompound of formula:

In certain embodiments, the cyanation step is palladium-catalyzed. Incertain embodiments, the palladium catalyst is Pd₂(dba)₂ with ligand. Incertain embodiments, the palladium catalyst is Pd(OAc)₂ with ligand. Incertain embodiments, the cyanation step is performed in the presence ofZn(CN)₂, Pd₂(dba)₃, and the ligand 1,1′-bis(diphenylphosphino)ferrocene(dppf). In certain embodiments, the amount of catalyst used ranges fromabout 0.1 mol % to about 20 mol %. Other palladium catalysts (includingligand) or sources of cyanide (e.g., NaCN, KCN, Cu(CN), K₄[Fe(CN)₆],tri-n-butyltincyanide) may also be used. In certain embodiments, thereaction is performed in DMF as the solvent. The reaction may beirradiated with microwaves in order to effect the transformation. Incertain embodiments, the reaction mixture is heated to effect thetransformation. In certain embodiments, the reaction is run at atemperature ranging from approximately 100° C. to approximately 150° C.In certain embodiments, the reaction mixture is heated to approximately110° C. In certain embodiments, the reaction mixture is heated toapproximately 120° C. In certain embodiments, the reaction is run atapproximately 130° C. In certain embodiments, the reaction mixture isirradiated with microwaves.

In certain embodiments, the invention provides a method of deprotectingthe protected amine of formula:

under suitable conditions to provide a compound of formula:

The condition for removing the protecting will depend on the protectinggroup being used. In certain embodiments, the invention provides amethod of deprotecting the protected amine of a compound of formula:

under suitable conditions to provide a compound of formula:

In certain embodiments, the deprotection is performed usingtrifluoroacetic acid. In certain embodiments, the solvent is methylenechloride. In certain embodiments, the deprotection reaction is performedat room temperature.

Synthesis of Eastern Portion

A new synthetic strategy for preparing eastern portion of A52 has alsobeen developed. This new scheme has less steps and yields increasedamounts of the final product B.4-(1-cyanocyclobutylamino)-2-fluoro-N-methylbenzamide B or an analogthereof may be prepared using any of the strategies shown below.

In certain embodiments, the ipso-substitution of the 4-fluoro moiety ofthe 2,4-difluorobenzyl amide M may be accomplished using4-methoxybenzylamine or another protected amine as shown below. Simpledeprotection of the amine followed by the Strecker reaction gavecompound B.

In certain embodiments, the method of synthesizing Compound B comprisesthe steps of:

(a) reacting a compound of formula:

with an amine of formula:

under suitable conditions to form a product of formula:

(b) deprotecting a compound of formula:

under suitable conditions to form a product of formula:

and

(c) reacting a compound of formula:

with

and a source of cyanide (CN) under suitable conditions to provide acompound of formula:

In certain embodiments, the invention provides a method of preparing theeastern portion of A52 comprising reacting a compound of formula:

wherein R₁ is a substituted or unsubstituted acyl moiety or —CN, with

under suitable conditions to provide a compound of formula:

In certain embodiments, R₁ is acyl. In certain embodiments, R₁ is

In certain embodiments, R₁ is

In certain embodiments, R₁ is —CN.

In certain embodiments, the method comprises reacting a compound offormula:

wherein R₁ is a substituted or unsubstituted acyl moiety or —CN, with

and a source of cyanide (CN) under suitable conditions to provide acompound of formula:

In certain embodiments, R₁ is acyl. In certain embodiments, R₁ is

In certain embodiments, R₁ is

In certain embodiments, the source of cyanide is NaCN. In certainembodiments, the source of cyanide is KCN.

In certain embodiments, the method comprises reacting a compound offormula:

with a protected amine of formula:

NH(PG)₂

wherein each PG is independently hydrogen or a suitablenitrogen-protecting group, under suitable conditions to form a productof formula:

In certain embodiments, the method comprises reacting a compound offormula:

with an amine of formula:

under suitable conditions to form a product of formula:

In certain embodiments, the reaction is carried out in DMSO as thesolvent. In certain embodiments, the reaction mixture is irradiated withmicrowaves. In certain embodiments, the reaction mixture is heated to atemperature ranging from approximately 150° C. to approximately 200° C.In certain embodiments, the reaction mixture is heated to approximately170° C. In certain embodiments, the reaction mixture is heated toapproximately 180° C. In certain embodiments, the reaction mixture isheated to approximately 190° C. Preferably, the conditions of thereaction are such that the substitution of the amine occurspredominately at the 4-position rather than the 2-position of the phenylring.

In certain embodiments, the invention provides a method of deprotectingthe amine. In certain embodiments, the method comprises deprotecting acompound of formula:

wherein each PG is independently hydrogen or a nitrogen-protectinggroup, under suitable conditions to form a product of formula:

The conditions for removing the protecting group will depend on theprotecting group being used. In certain particular embodiments, themethod comprises deprotecting a compound of formula:

under suitable conditions to form a product of formula:

In certain embodiments, the deprotection step is done in the presence oftrifluoroacetic acid. In certain embodiments, the deprotection step isdone with trifluoroacetic acid in dichloromethane.

In certain embodiments, the method comprises reducing a compound offormula:

under suitable conditions to form a product of formula:

wherein R₁ is a substituted or unsubstituted acyl moiety or —CN. Incertain embodiments, R₁ is acyl. In certain embodiments, R₁ is

In certain embodiments, R₁ is

In certain embodiments, R₁ is —CN. This reduction of the nitro group isdone in the presence of other functional groups which are susceptible toreduction. Preferably, the conditions of the reduction step are suchthat the nitro group is reduced without substantially affecting theother functional groups. In certain embodiments, the reduction is donewith dissolved iron. In certain embodiments, the reduction is performedusing iron powder (or other form of iron) dissolved in acetic acid (orother acid) and a solvent (e.g., ethyl acetate). In certain embodiments,at least 2 equivalents of iron are used. In certain embodiments,approximately 5 equivalents of iron are used. Other metals besides ironmay also be used in this reduction step. In certain embodiments, thereaction is performed at room temperature. In certain embodiments, thereaction mixture is heated. In certain embodiments, the reaction isperformed at approximately 60-75° C. In certain embodiments, thereaction is performed at approximately 65° C. In certain otherembodiments, the reduction of the nitro group is performed using a Raneynickel hydrogenation. In certain embodiments, the nitro group is reducedto the corresponding amine in the presence of Raney nickel in ethanol(or other alcohol) at 50 psi H₂.

Formation of Thiohydantoin

Once the two halves of the desired compound are prepare, they are thencoupled to form the resulting biarylthiohydantoin as shown below.

In certain embodiments, the invention provides a method of synthesizinga biarylthiohydantoin of formula:

wherein

n is an integer between 1 and 4, inclusive;

each R₁ is independently selected from the group consisting of hydrogen;halogen; cyclic or acyclic, substituted or unsubstituted, branched orunbranched aliphatic; cyclic or acyclic, substituted or unsubstituted,branched or unbranched heteroaliphatic; substituted or unsubstituted,branched or unbranched acyl; substituted or unsubstituted, branched orunbranched aryl; substituted or unsubstituted, branched or unbranchedheteroaryl; —OR_(A); —C(═O)R_(A); —CO₂R_(A); —CN; —SCN; —NCS; —SR_(A);—SOR_(A); —SO₂R_(A); —NO₂; —N₃; —N(R_(A))₂; —NHC(═O)R_(A);—NR_(G)C(═O)N(R_(A))₂; —OC(═O)OR_(A); —OC(═O)R_(A); —OC(═O)N(R_(A))₂;—NR_(A)C(═O)OR_(A); or —C(R_(A))₃; wherein each occurrence of R_(A) isindependently a hydrogen, a protecting group, an aliphatic moiety, aheteroaliphatic moiety, an acyl moiety; an aryl moiety; a heteroarylmoiety; alkoxy; aryloxy; alkylthio; arylthio; amino, alkylamino,dialkylamino, heteroaryloxy; or heteroarylthio moiety; and

R₂ is a substituted or unsubstituted aryl; or substituted orunsubstituted heteroaryl; comprising the step of coupling a substitutedpyridine of formula:

with a compound of formula:

under suitable conditions to form a product of formula:

In certain embodiments, the step of coupling is performed withapproximately 1 equivalent of each half of the molecule. In certainembodiments, the step of coupling is performed is with approximately 2-3equivalents of the substituted pyridine and approximately 1 equivalentof the other half of the molecule. In certain embodiments, the couplingis performed in DMF at approximately 80° C. with microwave irradiationfollowed by acid hydrolysis (e.g., HCl in methanol) of the intermediateimidohydantoin. In certain embodiments, the coupling is performed byreacting the two halves of the molecule with thiophosgene, followed byheating in N,N-dimethylacetamide at about 60° C., and finally followedby acid hydrolysis (e.g., HCl in methanol) of the intermediateimidohydantoin. In certain embodiments, the final product is optionallypurified. In certain embodiments, the final product is purified bycolumn chromatography. In certain embodiments, the final product ispurified by re-crystallization. In certain embodiments, the substitutedpyridine is of the formula:

In certain embodiments, the compound for coupling of formula:

In certain embodiments, the compound for coupling of formula:

The inventive methodology allows for a scaleable synthesis of A52 andother analogs thereof. In certain embodiments, approximately 10 grams ofthe final product are prepared using the inventive synthesis. In certainembodiments, approximately 20 grams of the final product are prepared.In certain embodiments, approximately 50 grams of the final product areprepared. In certain embodiments, approximately 100 grams of the finalproduct are prepared. In certain embodiments, approximately 200 grams ofthe final product are prepared. In certain embodiments, approximately500 grams of the final product are prepared. In certain embodiments,approximately 1000 grams of the final product are prepared. Theinventive synthesis also provides compound that is at least 90%, 95%,98%, 99%, or 99.9% pure. In certain embodiments, the synthesis providesa compound that is sufficiently pure that it could be formulated andadministered to humans or other animals. In certain embodiments, theresulting compound is used in veterinary medicine. In certainembodiments, the resulting compound is used for pre-clinical studies.

Intermediates

Not only does the invention provide methodology for preparingbiarylthiohydantions, but it also provides useful intermediates as well.

In certain embodiments, the invention provides a compound of formula:

In certain embodiments, the invention provides a compound of formula:

In certain embodiments, the invention provides a compound of formula:

wherein X is a halogen. In certain embodiments, X is bromine. In certainembodiments, X is iodine.

In certain embodiments, the invention provides a compound of formula:

wherein X is halogen. In certain embodiments, X is bromine. In certainembodiments, X is iodine.

In certain embodiments, the invention provides a compound of formula:

wherein X is halogen or —CN; and each PG is independently hydrogen or anitrogen protecting group. In certain embodiments, X is chlorine. Incertain embodiments, X is bromine. In certain embodiments, X is iodine.In certain embodiments, X is —CN. In certain embodiments, at least onePG is hydrogen. In certain embodiments, PG is benzyl. In certainembodiments, PG is methoxybenzyl. In certain embodiments, PG is4-methoxybenzyl.

In certain embodiments, the invention provides a compound of formula:

wherein X is halogen or —CN. In certain embodiments, X is chlorine. Incertain embodiments, X is bromine. In certain embodiments, X is iodine.In certain embodiments, X is —CN.

In certain embodiments, the invention provides a compound of formula:

In certain embodiments, the invention provides a compound of formula:

wherein each PG is independently hydrogen or a nitrogen protectinggroup. In certain embodiments, the invention provides a compound offormula:

In certain embodiments, the invention provides a compound of formula:

In certain embodiments, the invention provides a compound of formula:

These and other aspects of the present invention will be furtherappreciated upon consideration of the following Examples, which areintended to illustrate certain particular embodiments of the inventionbut are not intended to limit its scope, as defined by the claims.

EXAMPLES Example 1 Synthesis of A52

This example provides an alternative route to the two key intermediates,namely 3-(trifluoromethyl)-5-isothiocyanatopyridine-2-carbonitrile A and4-(1-cyano-1-cyclobutylamino)-2-fluoro-N-methylbenzamide B, as shown inthe retrosynthetic analysis in FIG. 1.

The route described below provides compound A through a shorter sequenceof steps from nitropyridone E (Scheme 1 below) by selective reduction ofthe nitro group using dissolved iron followed by palladium-catalyzedcyanation. The synthesis of intermediate A was further improved via thesequence of steps entailing chlorination of the 5-nitropyridine E,palladium-catalyzed cyanation (Chobanian et al., Tetrahedron Letters,2006, 47, 3303-3305) at carbon 2 to give G, and subsequent selectivereduction of the nitro group to the corresponding amine (Salvati, etal., Published US Patent Application, 2004/077605, which is incorporatedherein by reference), in the presence of the very active nitrile, usingdissolving iron in acetic acid to lead to amine H in a good yield.Finally, the conversion of the amine to the corresponding isothiocyanatewith thiophosgene in the presence of base concluded the synthesis of thewestern half of A52.

While the method above has shortened the synthesis by four steps, aswell as provided a better overall yield, another route was sought toavoid nitration by providing a more accessible precursor to the aminogroup. More reactive derivatives of C, such as5-iodo-3-trifluoro-2-pyridone I or the respective 5-bromo wereconsidered as preferred precursors to provide an anchoring position forthe amine in H. The amine at carbon 5 of H could be the result of thedisplacement of a bromide, triflate, iodide, or the like directlythrough nucleophilic aromatic substitution and/or through transitionmetal catalyzed amination, alkyl amination, or carbamoylation. The aminecould be a free one such as ammonia, or in a protected form such thatthe protecting group could be later removed to provide the desiredamine. Protecting groups of the amine could be chosen among those thatare removable by hydrogenolysis such as benzyl amine and itselectron-rich analogs such as methoxybenzylamine, preferably4-methoxybenzylamine. Another set of protected amines that are known toreact in a transition metal catalyzed coupling are active amides,carbamates, and amines that are released through the action of fluorideion on a silyl or silylalkyl amine. Exemplary carbamates useful in theinvention are tertiobutylcarbamate and benzylcarbamate. They react withiodopyridone under palladium-mediated catalysis.

Compound H is accessed through the following sequence of steps:iodination of 3-trifluoromethyl-2-pyridone C, chlorination of resultingpyridone to the respective 2-chloropyridine J, two successivePd-catalyzed substitutions, the first of which at position 5 on theiodide by a protected amine, and the second at position 2 whichintroduces the required cyano group; and lastly the removal of theprotecting group on the amine by trifluoroacetic acid, and formation ofthe corresponding thiocyanate. While longer than previous schemes, thisembodiment proved to be better at scaling up while requiring smalleramounts of catalyst and providing better yields of the desired finalproduct.

The iodination was performed following a described procedure (R. Kawai,M. Kimoto, S. Ikeda, T. Mitsui, M. Endo, S. Yokoyama and I. Hirao, J.Am. Chem Soc, 2005, 127, 17286-17295) to provide compound I. Then aslight modification of a published method (S. Kagabu, SyntheticCommunications, 2006, 36, 1235-1245) was used to accesschloroiodopyridine intermediate J. Microwave irradiation was used whichshortens the reaction time from four hours to 20 min. Subsequently, afirst transition metal assisted coupling (J. Kuethe, A. Wong, and I. W.Davies, J. Org. Chem., 2004, 69, 7752-7754) using only 3 mol % of thepalladium acetate catalyst involving the position 5 of the pyridiniumring activated with an iodide led to intermediate K. The latter, inturn, undergoes a palladium-assisted cyanation as previously executed inScheme 2, to provide the intermediate L with yields averaging 90%.Finally simple deprotection of the amine with concentratedtrifluoroacetic acid gave H in quantitative yield. The conversion of theamine to the isothiocyanate with thiophosgene concludes the preparationof the intermediate A.

Using Pd₂(dba)₃ and xantphos ligand in the presence of sodiumtertiobutoxide under refluxing toluene, selective substitution at theiodide site could be achieved in scaleable yields that are greater than85% (Scheme 3).

Improved Synthesis of the Right Half of A52, Intermediate B

A new synthesis of the right half of A52 has also been developed, namelya new method to prepare4-(1-cyanocyclobutylamino)-2-fluoro-N-methylbenzamide (B), with ashorter number of steps and that provides increased amounts of B. Asshown in Scheme 4, the fluorine atom in para-fluorobenzonitrile O isdisplaced by the not so nucleophilic amine N namely1-amino-1-cyanocyclobutane. But, due to the presence of an additionalnitrile in the final intermediate B, it should be possible andpreferable to displace the fluorine atom on the methyl2,4-difluorobenzoic ester Q. However, methyl 2,4-difluorobenzyl amide Mthough less active under the reaction conditions should provide a moredirect access and also ease the follow up functional modifications toreach N-methyl amide B.

Considering all these reactivity patterns, a route for the preparationof B in large amounts has been achieved (Scheme 5). By applyingmicrowave assistance, effective ipso-substitution of the 4-fluoride in2,4-difluorobenzyl amide M with paramethoxybenzylamine provided theamide S in about 20% yield (un-optimized). Simple deprotection of theamine and Strecker reaction with cyclobutanone gave key intermediate B.

Convergent Coupling to Yield A52

The final coupling step between intermediates A and B is achieved bymicrowave irradiation and cyclization to the biarylthiohydantoin A52(Scheme 6). Although 3 equivalents of A are required for the highestyields in this transformation, the un-reacted amine A can be recovered.

Another method to access A52 uses a different solvent at lowertemperature, but for a longer reaction time. Indeed, when 1.05 molarequivalents of amine A and 1.0 equivalent of amide B were mixed inN,N-dimethylacetamide, and the resulting mixture brought to 60° C. for 6to 14 hours, followed by acid hydrolysis of the intermediateimidohydantoin, A52 could be isolated in yields that are greater than75% (Scheme 7).

Experimental Section 2-cyano-5-nitro-3-trifluoromethylpyridine

Zinc cyanide (25 mg, 0.216 mmol, 1.2 eq) is added to the chloride (43mg, 0.180 mmol) solubilized in DMF (1 ml). The solution is degassed for10 minutes. Then the ligand dppf (20 mg, 0.036 mmol, 0.2 eq) is added.The solution is degassed again for 5 min. The catalyst Pd₂(dba)₃ (25 mg,0.027 mmol, 0.15 eq) is added, the solution is degassed for 5 moreminutes. The reaction mixture is then heated at 130° C. for 20 min in amicrowave. After filtration, the solvent is evaporated and the cruderesidue is purified by flash chromatography on silica gel (hexane/EtOAc)to afford 16 mg (40%) of the desired product.

¹H NMR (400 MHz, CDCl₃) δ 8.60 (d, J=2.5, 1H); 9.08 (d, J=2.5, 1H),

5-amino-2-cyano-3-trifluoromethylpyridine

2-cyano-5-nitro-3-trifluoromethylpyridine (7 mg, 0.032 mmol) isdissolved in 1:1 EtOAc/AcOH (1 mL) and heated to 65° C. Iron powder (9mg, 0.161 μmol, 5 eq, 325 mesh) is added and the mixture stirred for 2hours. The mixture is filtered through celite, and the filtrate isconcentrated under vacuo. The crude residue is purified by flashchromatography on silica gel (hexane/EtOAc) to afford 4 mg (67%) of thedesired product.

¹H NMR (400 MHz CDCl3) δ 7.20 (d, J=2.4 Hz, 1H), 8.22 (d, J=2.4 Hz, 1H).

5-iodo-3-trifluoromethyl-2-pyridinol

3-trifluoromethyl-2-pyridinol (25 g, 153.3 mmol) is dissolved inanhydrous CH₃CN (150 mL) and DMF (150 mL). N-iodosuccinimide (34.5 g,153 mmol) is then added. The reaction mixture is stirred at 80° C. for 2hours and cooled to room temperature. Aqueous 1 M NaHCO₃ (150 mL) isthen added to the cooled mixture. After stirring for 5 min, the solventsare evaporated to dryness. Water is added and the aqueous phase isextracted (×2) with dichloromethane. The organic phase is thenevaporated and the desired product is recrystallized in water to afford36.2 g (81%) of a white powder.

¹H NMR (500 MHz, CDCl₃) δ 7.85 (d, J=2.3, 1H); 7.98 (d, J=2.3, 1H),13.41 (br s, 1H); ¹³C NMR (250 MHz CDCl₃) δ 63.0, 121.4 (q,J_(C-F)=272.3 Hz), 122.2 (q, J_(C-F)=31.6 Hz), 144.4, 148.1 q,(J_(C-F)=5.0 Hz), 160.1.

2-chloro-5-iodo-3-trifluoromethylpyridine

To an ice-cold mixture of POCl₃ (1.60 mL) and DMF (1 mL) in a microwavevial, 5-iodo-3-trifluoromethyl-2-pyridinol (1 g, 3.47 mmol) is added.The vial is sealed and heated 20 min at 110° C. The reaction mixturecooled at room temperature is poured into ice cold water. The productprecipitates. The precipitate is filtered, washed with cold water anddried to afford 661 mg (62%) of a light brown powder.

¹H NMR (500 MHz CDCl₃) δ 8.32 (d, J=2.0 Hz, 1H), 8.81 (d, J=2.0 Hz, 1H).¹³C NMR (250 MHz CDCl₃) δ 89.4, 121.2 (q, J_(C-F)=273.3 Hz), 126.8 (q,J_(C-F)=33.6 Hz), 144.34, 148.5, 158.7.

2-choro-3-trifluoromethyl-N-paramethoxybenzylpyridin-5-amine K

2-choro-5-iodo-3-trifluoromethylpyridine is dried under vacuum. To aslurry of chloroiodpyridine (10 g, 32.6 mmol) in toluene (anhydrous) (98mL) is added sequentially. Pd(OAc)₂ (220 mg, 0.98 mmol, 0.03 eq),rac-BINAP (609 mg, 0.98 mmol, 0.03 eq) solid Cs₂CO₃ (53 g, 163 mmol, 5eq), paramethoxybenzylamine (4.05 mL, 30.9 mmol, 0.95 eq) andtriethylamine (0.41 mL, 2.93 mmol, 0.09 eq). The resulting slurry isdegassed (×2) by vacuum/Argon backfills. The mixture is heated to refluxovernight. The mixture is then cooled to room temperature and H₂O isadded. The layers are separated and the toluene layer is concentratedunder vacuo. The residue is purified by flash chromatography on silicagel (Hexane/EtOac; 95:5 to 30/70) to afford 4 g of white solid desiredcompound (40%).

¹H NMR (500 MHz CDCl₃) δ 3.81 (s, 3H), 4.29 (d, J=5.1 Hz, 2H), 4.32 (brs, 1H), 6.90 (d, J=8.1 Hz, 2H), 7.19 (d, J=2.9 Hz, 1H), 7.26 (d, J=8.1Hz, 2H), 7.92 (d, J=2.9 Hz, 1H). ¹³C NMR (250 MHz CDCl₃) δ 47.3, 55.4,114.3, 119.3 (q, J_(C-F)=5.1 Hz), 122.3 (q, J_(C-F)=272.9 Hz), 124.80(q, J_(C-F)=32.7 Hz), 128.8, 129.1, 135.1, 136.6, 142.9, 159.3.

Alternative Synthesis of Intermediate K:

A suspension of vacuum dried 2-choro-5-iodo-3-trifluoromethylpyridine(50 g, 163 mmol) in anhydrous toluene (1,500 mL) was treatedsequentially with Pd₂(dba)₃ (2.98 g, 3.25 mmol, 0.02 eq), Xantphos (5.65g, 9.76 mmol, 0.06 eq), solid t-BuONa (23.4 g, 243 mmol, 1.5 eq), andparamethoxybenzylamine (23.2 mL, 179 mmol, 1.1 eq). The resulting slurryis degassed by vacuum/argon backfills for 10 min. The mixture is thenquickly brought to reflux by a pre-heated oil bath. After 1.5 hours atthis temperature, the mixture was cooled to the ambiant, and the solidswere removed by filtration over a packed bed of celite and washed withtoluene. The filtrate was then diluted with EtOAc (200 mL), then washedwith H₂O. The organic layer was concentrated under reduced pressure gavean oily solid. Crystallization from DCM/Hexane gave (36.6 g, 71%) of Bas a light yellow solid.

Alternatively, smaller scales (5 to 10 gr of A) were purified by columnsilica gel chromatography using the gradient system Hexane-EtOAc 19-1 to3-7 (v-v). This gave yields in excess of 85% of B as a white solid.

2-cyano-3-trifluoromethyl-N-paramethoxybenzylpyridin-5-amine

Zinc cyanide (0.45 g, 3.80 mmol, 1.2 eq) is added to the chloride (1 g,3.16 mmol) solubilized in DMF (20 ml). The solution is degassed for 10minutes. Then the ligand dppf (0.35 g, 0.63 mmol, 0.2 eq) is added. Thesolution is degassed again for 5 min. The catalyst Pd₂(dba)₃ (0.29 g,0.32 mmol, 0.1 eq) is added, the solution is degassed for 5 moreminutes. The reaction mixture is then heated at 150° C. for 10 min.After filtration, the solvent is evaporated and the crude residue ispurified by flash chromatography on silica gel (hexane/EtOAc) to afford900 mg (93%) of a dark yellow oil.

¹H NMR (500 MHz CDCl3) δ 3.82 (s, 3H), 4.37 (d, J=5.3 Hz, 2H), 4.93 (brs, 1H), 6.92 (d, J=9.5, 2H), 7.08 (d, J=2.7 Hz, 1H), 7.25 (d, J=9.5,2H), 8.17 (d, J=2.7 Hz, 1H). ¹³C NMR (250 MHz CDCl3) δ 46.7, 55.4,113.9, 114.5, 115.9, 116.1, 122.0 (q, J_(C-F)=274.5 Hz), 128.0, 128.9,131.4 (q, J_(C-F)=33.1 Hz), 138.68, 145.9, 159.5.

5-amino-2-cyano-3-trifluoromethylpyridine H

TFA (1 mL) is added dropwise to a solution of pyridine L (83 mg, 0.27mmol) in dry DCM (0.5 mL) under argon. The solution is stirred overnightat room temperature. After completion of the reaction, the solvent isevaporated and the residue is purified by flash chromatography on silicagel (Hexane/EtOac) to afford the desired product quantitatively.

¹H NMR (500 MHz CDCl3) δ 7.20 (d, J=2.4 Hz, 1H), 8.22 (d, J=2.4 Hz, 1H).

Scale Up and Purification of H

For the larger scales, an improved process calls for dissolving pyridineL (53 g, 0.172 mol) in TFA/DCM (170 mL, 4:1) at room temperature. Uponreaction completion (approximately 2 hours at room temperature), thevolatiles were removed under reduced pressure. The residue is thendiluted with EtOAc (800 mL), and washed with saturated aqueous NaHCO₃.Vacuum concentration and precipitation from DCM-Hexane (1-2, v-v) gave arelatively clean product. Further washing with DCM gave pureintermediate H as a white solid (27.43 g, 85%).

Methyl 2,4-difluorobenzylamide

Methylamine 2M in THF (12.4 mL, 1.1 eq) is added to neat2,4-difluorobenzoyl chloride (4 g, 22.6 mmol). The reaction mixture isstirred overnight at room temperature. The solvent is evaporated, ethylacetate is added to solubilize the residue. The organic is washed withaqueous NaHCO₃, dried with Na₂SO₄, filtered and evaporated to afford thequantitatively the desired compound as a white powder.

¹H NMR (500 MHz CDCl3) δ 3.00 (d, J=4.8 Hz, 3H), 6.84 (m, J=2.3; 10.3Hz, 1H), 6.97 (m, J=2.3; 8.2 Hz, 1H), 8.08 (td, J=6.8; 8.9 Hz, 1H)

¹³C NMR (100 MHz CDCl3) δ 27.0, 104.3 (d, J=26.0 Hz), 104.6 (d, J=25.9Hz), 112.4 (dd, J=21.2; 3.1 Hz), 118.1 (dd, J=12.4; 3.8 Hz), 133.7 (dd,J=10.1; 3.9 Hz), 162.9 (dd, J=381.1; 12.3 Hz), 163.5.

Methyl 2-fluoro-4-paramethoxybenzylamine-benzylamide

Paramethoxybenzylamine (0.069 mL, 0.548 mmol, 2 eq) is added to methyl2,4-difluorobenzylamide (47 mg, 0.274 mmol) dissolved indimethylsulfoxide (0.5 mL). The reaction mixture is heated at 190° C.for 20 min in a microwave. After completion the solvent is evaporatedand the residue is purified by flash chromatography on silica gel(hexane/ethyl acetate) to give 18 mg (20%) of the desired product.

¹H NMR (500 MHz CDCl3) δ 2.98 (d, J=4.5 Hz, 3H), 3.81 (s, 3H), 4.26 (d,J=5.3 Hz, 2H), 4.47 (br s, 1H), 6.23 (dd, J=2.2; 15.1 Hz, 1H), 6.45 (dd,J=2.2; 8.7 Hz, 1H), 6.58 (br s, 1H), 6.89 (d, J=8.7 Hz, 2H), 7.25 (d,J=8.7 Hz, 2H), 7.91 (t, J=9.0 Hz, 1H). ¹³C NMR (500 MHz CDCl3) δ 26.6,47.3, 55.3, 98.2 (d, J=29.7 Hz), 109.25, 114.4, 128.6, 129.9, 133.1 (d,J=4.5 Hz), 152.3 (d, J=12.5 Hz), 159.1, 161.5, 163.9 (d, J=244 Hz),164.5.

Methyl 4-amino-2-fluoro-benzylamide

TFA (1 mL) is added dropwise to a solution of methylamide (60 mg, 0.21mmol) in dry DCM (0.5 mL) under argon. The solution is stirred overnightat room temperature. After completion of the reaction, the solvent isevaporated and the residue is purified by flash chromatography on silicagel (Hexane/EtOac) to afford the desired product quantitatively.

¹H NMR (500 MHz CDCl3) δ 2.98 (d, J=4.8 Hz, 3H), 4.15 (br s, 2H), 6.32(d, J=14.3 Hz, 1H), 6.48 (d, J=8.2 Hz, 1H), 6.61 (br s, 1H), 7.90 (dd,J=8.6 Hz, 1H), ¹³C NMR (500 MHz CDCl3) δ 26.63, 100.8 (d, J=28.8 Hz),110.3 (d, J=244.6 Hz), 110.9, 133.3 (d, J=4.3 Hz), 151.4 (d, J=12.5 Hz),162.2 (d, J=244.6 Hz), 164.3 (d, J=3.5 Hz).

Synthesis ofN-methyl-4-[7-(6-cyano-5-trifluoromethylpyridin-2-yl)-8-oxo-6-thioxo-5,7-diazaspiro[3.4]octan-5-yl]-2-fluorobenzamide(A52) One Pot Small Scale (2.8 gr) Thiohydantoin Formation in DMF

Thiophosgene (1.2 mL, 1.16 eq, 15.6 mmol) is added dropwise to asolution of 5-amino-2-cyano-3-trifluoromethylpyridine (2.8 g, 1.1 eq,15.0 mmol) and N-methyl-4-(1-cyanocyclobutylamino)-2-fluorobenzamide(3.35 g, 13.5 mmol) in dry DMF (25 mL) under Argon. The solution isstirred overnight at 60° C. To this mixture were added MeOH (60 mL) andaq. 2M HCl (30 mL), then the mixture was reflux for 2 h. After coolingto rt, the mixture was poured into ice water (100 mL) and extracted withEtOAc (3×60 mL). The organic layer was dried over Mg₂SO₄, concentratedand chromatographed on silica gel using 5% acetone in DCM to yield thedesired product (2.65 g, 41%).

Alternative Synthesis of A52

Thiophosgene (1.23 mL, 16.0 mmol) is added dropwise to a solution of5-amino-2-cyano-3-trifluoromethylpyridine (3.0 g, 16.0 mmol) andN-methyl-4-(1-cyanocyclobutylamino)-2-fluorobenzamide (3.96 g, 16.0mmol) in dry DMA (35 mL) under Argon. The solution is stirred overnightat 60° C. To this mixture were added MeOH (60 mL) and aq. 2M HCl (30mL), then it was brought to reflux temperature for 2 h. After coolingdown to the ambiant, the mixture was poured into ice water (100 mL) andextracted with EtOAc (3×60 mL). The organic layer was dried over Mg₂SO₄,filtered over celite, and concentrated under reduced pressure. Silicagel chromatography using DCM/-acetone 19-1 (v-v) yielded the desiredproduct (5.78 g, 76%).

Scale Up.

Thiophosgene (5.48 mL, 1.05 eq, 70.9 mmol) is added dropwise to asolution of 5-amino-2-cyano-3-trifluoromethylpyridine (13.27 g, 1.05 eq,70.9 mmol) and N-methyl-4-(1-cyanocyclobutylamino)-2-fluorobenzamide(16.7 g, 67.5 mmol) in dry DMA (110 mL) under Argon at 0° C. After 10min, the solution was heated up to 60° C. and allowed to stir at thattemperature for an overnight period. This was then diluted with MeOH(200 mL) and treated with aq. 2M HCl (140 mL), then the mixture wasrefluxed for 2 h. After cooling down to RT, the mixture was poured intoice water (500 mL), and filtered over buchner. The solid wasrecrystallized from DCM/EtOH to get desired product (20.6 g, 64%).

Other Embodiments

The foregoing has been a description of certain non-limiting preferredembodiments of the invention. Those of ordinary skill in the art willappreciate that various changes and modifications to this descriptionmay be made without departing from the spirit or scope of the presentinvention, as defined in the following claims.

1.-16. (canceled)
 17. A method of synthesizing a substituted pyridine offormula:

the method comprising steps of: (a) halogenating a compound of formula:

under suitable conditions to provide a compound of formula:

wherein X is bromine or iodine; (b) chlorinating the resultinghalogenated compound of step (a) under suitable conditions to provide acompound of formula:

wherein X is bromine or iodine; (c) aminating the resulting compound ofstep (b) under suitable conditions to provide a compound of formula:

(d) cyanating the resulting 2-chloropyridine of step (c) under suitableconditions to provide a compound of formula:

(e) deprotecting the amine of the compound of step (d) under suitableconditions to provide a compound of formula:

and (f) converting the 5-aminopyridine of step (e) under suitableconditions to the corresponding isothiocyanate of formula:

18.-23. (canceled)
 24. A method of synthesizing a substituted pyridineof formula:

the method comprising: aminating a compound of formula:

wherein X is bromine or iodine, under suitable conditions to provide acompound of formula:


25. The method of claim 24, wherein the step of aminating is performedusing pMBnNH₂.
 26. The method of claim 24, wherein X is I.
 27. Themethod of claim 24, wherein the step of aminating is performed in thepresence of a transition metal catalyst and an amine.
 28. The method ofclaim 24, wherein the step of aminating is performed in the presence ofPd(OAc)₂, BINAP, Et₃N, and Cs₂CO₃.
 29. The method of claim 24, whereinthe step of aminating is performed in the presence of Pd₂(dba)₃,Xantphos, and sodium tert-butoxide.
 30. The method of claim 24, whereinthe step of aminating comprises irradiating the reaction mixture withmicrowaves.
 31. A method of synthesizing a substituted pyridine offormula:

the method comprising: cyanating a compound of formula:

under suitable conditions to provide a compound of formula:


32. The method of claim 31, wherein the step of cyanating is performedusing a transition metal catalyst and a source of CN.
 33. The method ofclaim 31, wherein the step of cyanating is performed using Zn(CN)₂,Pd₂(dba)₃, and 1,1′-bis(diphenylphosphino)ferrocene (dppf).
 34. Themethod of claim 31, wherein the step of cyanating comprises irradiatingthe reaction mixture with microwaves.
 35. A method of synthesizing acompound of formula:

the method comprising: deprotecting the protected amine of a compound offormula:

under suitable conditions to provide a compound of formula:


36. The method of claim 35, wherein the step of deprotecting isperformed using trifluoroacetic acid (TFA). 37.-64. (canceled)